It takes 49 minutes for 9 people to paint 9 walls. How many minutes does it take 17 people to paint 17 walls?
Solution: Imagine that each person is assigned one wall, and all 9 people begin painting at the same time. Since everyone will finish painting their assigned wall after 49 minutes, it takes one person 49 minutes to paint one wall. If we have 17 people and 17 walls, we can again assign one wall to each person. Everyone will take 49 minutes to paint their assigned wall. In other words, it takes 49 minutes for 17 people to paint 17 walls.